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    <title>Document</title>
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    <script>
    var a={n:1};
    var b=a;
    a.x=a={n:2};
    console.log(a.n,b.n);//2,1
    console.log(a.x,b.x);  //undefined {n:2}
//     2 1
// undefined {n:2}
// 考察点：运算符的优先级和堆内存  
    </script>
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